Method of and means for flowing oil wells



G. M. WELLS METHOD OF AND MEANS FOR FIJOWING OIL WELLS Filed March 2,1957 gjgd June 7, 1938.

CONCRETE lNvENToR ofggef l/lls BY 4?/ M; @1547K ATTORNEYS Patented June7, 1938 PATENT OFFICE METHOD 0F AND MEANS FOR FLOWING OIL WELLS GeorgeM. Wells, Upper Montclair, N. J.

Application March 2, 1937, Serial No. 128,561

7 Claims.

My invention relates to a method of and means for flowing oil wells.

An object of my invention is to flow petroleum from wells which couldnot be flowed by methods available heretofore, and to increase the rateof flow as well as the length of time over which a. well will ow afterit has been brought in, thereby increasing the total amount of petroleumrecoverable from a well.

More particularly, my invention has as an object to obtain petroleumfree from sand, by employing filtering means that prevents the petroleumbearing formations from being removed along with the petroleum, andwhich means also does not clog with sand so as to stop the flow.

An additional object of my invention is to provide a method utilizablein connection with wells that are drilled with a heavy circulatingdrilling uid that is retained in the well in a circulating conditionwhen the well is not being flowed. n

'In drilling an oil well and preparing the same for flowing petroleumtherefrom, the common practice is to drill down through the variousformations until one or more strata are reached that contain petroleumthat it is desired to remove. These strata containing the petroleum aregenerally composed of sand, shales or other porous material containingsmall voids. The petroleum generally occurs as a fluid saturating or atleast partially filling the voids in the porous material. The petroleumin such strata is generally under a great pressure. As the petroleum isremoved through the Well it flows under pressure through the porousformation towards the well. f

At all times during a drilling operation and subsequently except whenthe well is being flowed, it is necessary to have the well filled with aheavy viscous mud, termed drilling fluid, whichv is circulated by pumps.It is this circulating drilling uid that removes the strata cuttingsAthat are cut away by the drilling tool or any other strata material thatmay be in the well due to slumng or cavings. .At all times, while thedrilling fluid`is in the well, it is essential that the fluid should bekept in circulation in order to prevent any vstrata particles in thefluid from settling out. If a given critical velocity were notmaintained, any strata particles in the fluid would be deposited at thebottom of the well and would have to be drilled out again.

When a petroleum bearing stratum is reached in the drilling, the weightof the column of the drilling uid in the well exerts a force which (Cl.16S-21) acts in opposition to the pressure on the petroleum in theporous stratum, and as long as the drilling fluid is present, thepetroleum is prevented from flowing through the stratum into the well.

In accordance with thecommon practice of flowing a well, the drillingapparatus is withdrawn after a petroleum bearing stratum is reached; thecasing is then cemented, the well under-teamed and a pipe is inserted atthe end of which is a screen having very small openings 10 which areintended to filter sand from the petroleum. The circulating drillingfluid is then gradually replaced by water and the pressure ex ertedagainst the petroleum in the porous stratum will be progressivelylessened because 15 of the lower specific gravity of the Water. Thisreduced pressure is generally such as to permit the petroleum to flowinto the well through the porous formation.

The sand of the porous stratum disintegrates 20 or moves under the flowof the petroleum. Before the flow is started, the pressure exerted bythe drilling fluid holds the porous sand formation in its originalposition However', when this pressure is lowered by replacing thedrilling fluid with water, and during the time the petroleum is flowingthrough the stratum, there is nothing to hold these formations inposition. There is often an initial caving of the sand against thescreen, or a bodily movement of a large mass of sand mixed with the mudthat has penetrated into the formation, which moves against the screen.Particularly is this the case when the petroleum is under great pressureand when the initial velocity of the petroleum is relatively high.

When petroleum flows through the stratum to the well, it also carriessand with it, and if the screen has not become clogged by an initialcaving, it is often clogged by the sand flowing with the petroleum. As aresult, the flow of petroleum 40 through the screen and into the-pipe isconsiderably reduced or stopped entirely. Numerous instances are ofrecord in which-a Well does not Y flow at all, or flows freely at firstfollowed by a quick decrease until the'flow is small or nil.

If the openings in the screen are made suiflciently small so as tofilter out most of the sand, the small openings are easily clogged withsand particles and mud. During the drilling operation a certain amountof the drilling fluid penetrates the porous formation, and the mudparticles ofthe drilling fluid, which are in the formation, are notremoved by the washing operation. As the petroleum moves into the wellthrough the stratum, it brings with it these fine LL n Before a lteringaction can he estao 'shed by the l r ger particles the screen openingsgenerally will have been cut to such a large size ever t larger sandparticles are restrained a ld there is no filtering action whatsoever.

lin screens having larger openings peirron leurs Aflows at a greatervelocity and carries a larger amount of sand particles through the "lgs,both of which augment the cutting network ci sand. particles could bebuilt up around the screen by employing a screen having large openingswhich permits the mud and small particles to pass through the screeninitially and exclude only the larger sand` particles. ln suchinstances, however, by the time such a condition has been established,the quantity of sand which has passed through .the screen is usually sogreat that the screen is cut so that the openings are not able to evenhold bacia the larger sand particles. Y

-he employment oi a screen as a filtering medium, therefore, gives riseto a dilemma in which the use oi openings of any size have suchdisadvantages as to render a screen a very undesirable filtering meansas compared withthat available in accordance with my invention.

ln the usual prior practice, after a screen has become clogged, anattempt is iirst made to remove the screen by pulling it out andinserting a new screen. The sand in the formation, however, usually hasbecome packed against the screen so tightly that the screen stlclis andcannot be removed. llf the well is to be nov/ed further or drilleddeeper, it is necessary-to out out .the screen and remove it in pieces.This usually proves to be a tedious and expensive operation.

I have heretofore proposed a method of flowing an oil Well by placingiron or steel balls, or equivalent material, in the wel] to hold theporous l formation in position and prevent lt from caving. The ballsalso act as an effective filtering medium for excluding the sand fromthe petroleum. By that method, the well can be iiowedA at high ratesover a long period of time, and petroleum obtained free from sand.

That method is particularly suitable when the petroleum bearing stratumis of relatively small depth. When the stratum is relatively deep theiron or steel balls tend to move down through the sand stratum untilthey are supported hy a firm material. In employing that method forowing petroleum from a. relatively deep sand stratum, a larger quantityof balls is necessary.

I have now discovered that all 'of the unobvi ous advantages of mypreviously proposed method may be availed of, and that the disadvantagesthereof may be eliminated if the balls are confined by a perforatedrestraining means. By such a means the balls are held immovable in ailxed position Within `the well and cannot move in the sand formation.The method is suitable in y process.

accordance the illust embodiment of my inyen .on sh wn in :e the Well isdrilled to a petroleum bearing which it is desired to .low and thecasing is cemented in accordance voti?. the procedure well understoodthe art. A pipe, closed the bottom having the lower end perforated, ispartially ,lied w ii a sufficient quantity of iron or steel balls to'lul the portion the pipe adjaw cent perforations the lower end andusually extend somewhat above the perioratlons. The pipe is then loweredinto the well so that the perforated portion extends into the potro leumbearing stratum. The drilling is then gradually replaced by Water andbecause of the deoreased'pressure on the petroleum in the stratum, dueto the lower spe c gravity of water, the petroleum begins to YElow infrom the stratum, through the perforations, through the voids the balls,'and up 'through the pipe.

lt is also possible to insert the perforated pipe into the well withoutthe balls, and to pour the halls into the pipe alter it has been placedin the well.

The petroleum initially flowing 'from the formation when the v/ell isbrought in usually car ries sand and mud with The particles of sand varyin size, and the larger particles become entrappecl in the voids in theballs. As the voids "become filled with the larger sand particles, theseparticles in turn hold back smaller sand particles. This continues untila perfect itering network oi sand particles is formed in the voids ofthe balls, which holds back sand particles of all sizes. After the wellhas been flowing for a short time, this filtering network is establishedand is effective in holding back even the finest sand particles, and asa result the well flows clear of sand.

'During the initial flow after the well is brought in, While a filter ofsand particles is being established in the voids of the balls, the nesand and the mud is not held back and reaches the surface of the well.The mixture of mud and other fine particles, which would normally clogand seal the small openings in a screen, will have initially passedthrough the voids in the balls. All of the mud in the formation willhave flowed out of the well by the time the flnal illtering network thatexcludes smaller sand particles is established. The initial ow ofpetroleum contains sand, but this is inconsequential as compared withthe Aflow that is subsequently obtained free from sand.

In view of my explanation, it will be understood that materials of arelatively low specific gravity, such as gravel or crushed rocks, couldnot be successfully employed as a ltering medium; such materials are notheavy enough to be held in position in a perforated restraining means.Filtering materials having a specific gravity of the same order as thespecic gravity of th'e sand particles would be moved, or even raised tothe surface, by the flowing petroleum, because velocities of thepetroleum which are suflicient to flow the sand particles through astrata are sufficient to flow material of similar specific gravitybeingemployed as a filtering medium; By employing iron or steel balls asa filtering medium, I am enabled to flow the well free from sand, at anincreased rate, and over a long period of time.

Because of the large number of balls and the many voids therein throughwhich the flow of the petroleum is distributed, the petroleum flowsthrough the voids at a relatively low velocity, andany cutting action ofthe sand that originally flows through the balls is minimized. Further,due to the hardness of the balls, they are not cut as readily as ascreen. The flow of the sand is also arrested sufficiently before anycutting'` takes place that would interfere withthe action Ivhavedescribed.

Other advantages are also obtained by using iron or steel balls. Duringthe time the filter network of sand particles is being established inthe voids of the balls, and subsequently during the continued filteringaction, it is essential that the lter structure be preserved. Anymovement of the balls would disturb the filter and release the sand inthe voids of the balls. This, of course, is undesirable because thepetroleum would not only contain this released sand, but also becausethe filter Vnetwork would be destroyedand would have to bere-establlished. Because of the high specific gravity of the balls theirweight holds them firmly and securely in the perforated restrainingmeans and they resist movement that would be imparted to material ofless specific gravity by an unevenness in the pressure of the flow.

In accordance with the illustrative example shown in Figure 2 the oilwell is provided with a lcasing that extends through a petroleum bearingstratum. At a suitable point in the casing, generally near the bottombut at any point in the petroleum bearing stratum, the casing is sealedby cementing a plug therein according to procedures well known in theart. The casing is then perforated above the plug and adjacent thepetroleum bearing stratum. During the perforating and at all times priorthereto, the drilling fluid .is circulating and the weight of the fluidprevents the petroleum from entering n so through the perforations inthecasing. Iron or steel balls are then poured into the casing; theydescend through the circulating uid and rest upon the cement plug,extending upwardly in the casing adiacentthe perforations and into theimperforate portion of the casing if desired. Water is then substitutedfor the drilling fluid and the pressure decreased in the usual manner;the petroleum will then begin to flow in from the stratum. It enters theperforations in the casing and then flows between the voids in the ballspassing upwardly .out through the casing or through a center pipe thatis often employed for that purpose. The sand which initially flowsthrough the stratum with the petroleum` and enters the perforations inthe casing will become lodged in the voids between the balls and afiltering network will be built up in the balls which will effectivelyeliminate the flow of further sand as has been described in detailheretofore.

drilling fluid as soon as the balls are inserted into the casing, andthey will settle in position in the perforated restraining means.Filtering material having a lower specific gravity, for example, graveland crushed rock, could not be inserted in the well in this manneragainst the ilow of the drilling fluid because the velocities of thedrilling fluid which would keep strata material in circulation wouldalso circulate such filtering material. A particular reason for keepingthe fluid circulating at a velocity that will keep strata material insuspension, is to prevent it from settling in the voids of the ballsbefore the well is washed and brought in. If the strata material settlesin the voids, it is very difiicult to remove by washing.

Although the balls are heavy enough to be inserted against the velocitynormally maintained in the circulating drilling fluid, nevertheless theballs are not so heavy as to prevent their .subsequent removal by atemporary higher velocity of the fluid specially introduced for thatpurpose.

In many instances a easing extends through a number of petroleum bearingstrata. In accordance with my invention, a plug is cemented at eachstratum it is desired to flow. The casing is then perforated adjacentthe stratum and iron or steel balls are introduced as described above.

In accordance with my invention, it is possible to re-establish the flowin oil wells having clogged screens by perforating the screen and thenintroducing iron or steel balls to iill the screen and the tube insidethereof.

It is particularly desirable that as the well is brought in, the flowshould be established in such a manner that it will continue uniformlyover a long period of time, and not necessitate repeated adjustments orchanges in the equipment used in flowing the wells. I found that theiron and steel balls employed in accordance with my invention accomplishthis purpose admirably with much more uniformity and dependability ofresults than has been obtained heretofore.

By means of my invention it is possible to flow petroleum from a stratacontaining such fine sand that it has heretofore not been regarded asfeasible to remove the petroleum therefrom by methods heretoforeavailable. The filtering network provided by the balls and the sandentrapped therein, operates so effectively that an extremely fine sandstratum may be flowed, and

petroleum obtained from a stratum which has` heretofore been regarded asunowable.

The size of the balls may vary over wide limits depending upon the sizeof the well, the rate at which itzis to be flowed, the character of theformation, and the size of the sand. When the i sand particles areextremely fine I have obtained adjusted so as to be smaller than thesize of the balls.

Heavy material other than iron or steel balls, having the capability oi'forming suitable voids may be used in my invention as an equivalent ofballs, provided such material has the necessary high specific gravity inorder that it may function in the manner pointed out heretofore. Suchheavy material has a specific gravity of twice. or even two and one-halftimes, the specific gravity of the formation. Such material willpreferably have a specific gravity of sin, or even seven to eight. Othermetals, such as lead, or alloys having the prerequisite speciiic gravitymay be used. Other heavy materials suc-h as ores of the requisitespecific gravity and hardness may be employed.

The shape of the material may also vary. Material having a uniformitycoemcient of substantial unity yis preferred. Cl@he volume of the voidsin such material will be a maximum and the voids will be uniformlydistributed. This permits the largest quantity oi petroleum 'to 'flowthrough the voids and due to the uniformity and even distribution of thevoids the filter network of sand particles will be formed more readily.The surface need not necessarily be spherical and by the expressionvoid-forming subdivided material used hereinafter, i refer to anymaterial, which when brought together,` will leave suitable voidsbetween the individual pieces of the material. A subdivided materialhaving a uniiormity coemcient of unity represents the ideal.

it will be appreciated that many other modifications may be made in theexact procedure of flowing a Weil in accordance with my invention,depending upon the type of formation and the condition of the well atthe time the flow isstarted. All such procedures in which void-formingmaterial of a high specific gravity is introduced in a well and retainedin position therein are intended to be Within the scope oi my invention,as set forth in the following claims.

`I claim:

1. In an oil well, an apparatus for flowing petroleum from the well andfor maintaining the ilow against stoppage comprising a. rigid perforatedrestraining means in said oil well adjacent the petroleum bearingstratum thereof, and a void forming sub-divided material held in saidrestraining means and adjacent said perforations, said void formingmaterial having a speciiic gravity of at least twice the specic gravityof the petroleum bearing stratum, whereby said void forming material isheld by the action of gravity in said perforated restraining means andis undisturbed in its ltering action by petroleum iiowing through saidvoid-forming material at a velocity that normally causes sand to flowwith petroleum.

2. In an oil` well, an apparatus for flowing petroleum from the Well andfor maintaining the iiow against stoppage comprising a rigid perforatedrestraining means in saidoil Well adjacent the petroleum bearing stratumthereof, and ironA balls held in said restraining means adjacent saidperforations whereby said iron balls are held by the action of gravityin said perforated restraining means and are undisturbed in theirilltering action by petroleum owlng through the vvoids aiiaeee in saidiron balls at a 'velocity that normally causes sand to ow withpetroleum.

3. In a method of flowing an oil well drilled to a petroleum bearingstratum and containing a circulating drilling iluid, the stepscomprising inserting into said well within a rigid perforatedrestraining means, a void-forming sub-divided material having a specificgravity of at least twice the specific gravity of the petroleum bearingstratum, and then washing said well to remove the drilling iiuid,whereby said material is restrained against movement in the well andtilters the petroleum flowing therethrough.

e. In a method of flowing an oil well drilled to a petroleum bearingstratum and containing a circulating drilling fluid, the stepscomprising inserting iron balls into .said well within a rigidperforated restraining means, and then washing said well to remove thedrilling fluid, whereby said iron balls are restrained against movementin the well and lter the petroleum flowing therethrough. y

5. lin a method o flowing an oil well drilled to a petroleum bearingstratum and containing a circulating drilling i'luid, the stepscomprising inserting into said well a perforated restraining means and avoid-forming sub-divided material having a specic gravity of at leasttwice the specific gravity of the petroleum bearing stratum, whichmaterial is held in said restraining means, and then washing said wellto remove the drilling uld, whereby said material is restrained againstmovement in the well and filters the petroleum flowing therethrough.

6. Themethod of flowing an oil Well which contains a rigidcircumferential restraining means and in which a drilling uid iscirculating,

the steps ycomprising sealing said restraining means adjacent apetroleum bearing stratum, perforating said restraining means,introducing thereinto a void-forming sub-divided material having aspecific gravity of at least twice the specific gravity of the petroleumbearing stratum, and then washing said well to remove the'drilling uid,whereby said material is restrained against movement in the well andfil-

